Consciousness and Memory

There is a semantic problem that I have often
run into when discussing memory and consciousness.
People usually have distinct conceptualizations of
"memory" and "consciousness" that do not
overlap. In what follows I will try to bring memory
and consciousness together. There are famous examples
from history in which two apparently unrelated
phenomena were found to be related. For example,
Newton realized that the same force that holds people
to the ground is what holds the Earth's Moon and the
planets in their orbits.

Part of the problem is that memory has two sides to
it: the storage side and the utilization side. In
general, if I say "memory is at the center of the
problem of consciousnes" people are going to think
I mean that storage of memories is central to
consciousness. As described below, I like Edelman's
theory of consciousness and and in his theory the
storage of memories is important to the construction
of human consciousness. However, on a second-to-second
basis, ongoing conscious experience is only dependent
on access to existing memory stores. This idea shocks
most people because they imagine that consciousness is
made possible by some kind of memoryless system like a
TV camera collecting input and sending it right to a
TV screen for viewing.

We need to be clear about the nature of memory and
consciousness. In the case of memory, we all agree
that it is possible to have memories that are due to
experiences from either long ago (say, years in the
past) or from more recently (say, 30 minutes ago).
Neurobiologists often make a distinction between
short-term and long-term memory. Most people are
fairly comfortable with the idea of memories that are
years, days, or maybe 5 minutes old. Some Long-term
memory mechanisms require relatively slow processes
such as alterations in gene transcription and
formation of new synapses. Some short-term memory
processes seem to just involve quick changes to
synapses such as alterations in protein
phosphorylation. In general, there are ways of
converting some shorter-term memories into longer-term
memories. An interesting question is how the brain
"decides" which experiences are important enough
to be remembered.

Let's push things under 5 minutes. If I tell you a
phone number you can repeat it back to me. Most
neurobiologists are comfortable with the idea of
"immediate memory" or "working memory". In the
case of a phone number you might only remember it long
enough to make a phone call, maybe 10 seconds after
someone tells it to you. I have never read the book The Man Who Mistook His Wife For A Hat : And Other Clinical Tales by
Oliver Sacks, but my guess is that most people who are
described as having "lost the ability to form
memories" still have "immediate memory" or
"working memory".

Can we place memory in an even shorter time frame?
What if I say a single number and ask you to repeat it
back to me? Would you be willing to say that you are
able to act on a memory of what you heard me say when
you immediately repeat something I have just said?
Most people start to get uneasy at this point. You
might think, "No, this is not memory. I have simply
held what you said in my conscious awareness and
repeated what I heard you say. My act of repeating
what you said did not involve the storage of a
memory." We could adopt a definition of memory that
includes the idea that something is only a memory if
it can pass out of consciousness and then be brought
back out of memory storage to again become part of our
conscious thoughts, but I think this is an artificial
limitation. As discussed below, some memory processes
do not involve consciousness at all. In any case, I do
not want to force upon you the idea that some forms of
memory can be stored in a fraction of a second. My
goal here is to get you to think about the idea that
you can certainly access your memories very quickly.

Most people with normal brain structure and function
are able to conceptualize three divisions of time:
past, present, future. People usually think of
consciousness as existing in the present. We sometimes
describe the contents of consciousness as "present
experience". This contrasts with what we think of
as memory. We think of memory as being due to
experiences that were in the past, not the present.
But when we recall memories that act of recall CAN contribute to
present experience. What happens if a person is in a
sensory deprivation chamber? Is their consciousness
generated by their memories? You might argue that
there is some non-memory part of the brain that that
generates consciousness in the absence of sensory
input, but would anything that produces consciousness
be independent of previously stored memories?

In Edelman's trilogy of books about the mind, the
book about consciousness is called "The Remembered
Present". The title of the book automatically forces
us to wonder if it make sense to think of some form of
memory as being what we experience as the present
contents of our consciousness. Now, if you are
dogmatically attached to the idea that memories are
the domain of past experience while consciousness is
the domain of the present, then you automatically
reject the notion that memory can have anything
fundamental to do with consciousness. You may also get
mad at someone who tries to suggest such a thing.
"You are just playing games, trying to redefine the
meaning of the terms memory and consciousness! Stop
it! We all KNOW that consciousness is not memory."

Simple neuronal networks are simple input-output
devices. A sensory stimulus is used to trigger some
output such as a muscle contraction. In a neuronal
network with no memory, the same input to the network
will always cause the same output. We can define
memory storage as being a process that causes a change
in the input-output relationship that a neuronal
network expresses. Once a neuronal network has had its
structure and function modified by the storage of a
memory, all future activity of that network is to some
degree an expression of that memory. Is consciousness
the expression of certain types of memories?

An important division in memory types is the division
between "explicit" and "procedural" memories.
Sometimes these categories are called
"declarative" and "implicit" memory,
respectively. We can also call these two broad
categories "conscious" and "unconscious"
memory systems. Learning to ride a bike is a good
example where "procedural" memories are formed. We
are not conscious of all of the adjustments that our
nervous system makes when we learn to ride a bike.
Much of the learning of bike riding is accomplished by
changes to neuronal networks that do not enter into
our conscious awareness. We can conclude that there
are neuronal networks in our brain that can store
memories and that do not participate in consciousness
while there are other networks that can store memories
that can enter into conscious experience.

What is the relationship between unconscious brain
processes and conscious brain processes? Are these two
distinct sets of brain processes or is there some
interaction and interdependence? I think it is clear
that information can pass back and forth between those
neuronal nets that can and do make our conscious
experiences and those networks that are not directly
involved in producing conscious experience..... but we
often do not think about this because our unconscious
brain processes are by definition outside of our
conscious thoughts. People such as George Lakoff have
struggled mightily to make the point that our
unconscious brain processes heavily influence our
consciousness. I like an analogy to an iceberg.
Consciousness is the tip of the iceberg and its
ability to rise up into the air of consciousness is
totally dependent on the vast amount of unexperienced
unconscious brain activity that supports it. In
particular, a bit of introspection and thinking should
convince people that their explicit memories depend
heavily on unconscious memory processes. When a child
learns an alphabet, neuronal networks are shaped in
the brain and memories are stored that allow
recognition of spoken words and that allow the child
to say letters and words. When we speak, we are not
consciously aware of the vast amount of neuronal
network activity involved in how we recognize and
understand the words we hear and how we make our
bodies say words and what we want to say. If
consciousness is an expression of memory utilization,
it is only an expression of a subset of our memories.
Only certain parts of the brain are expected to
contribute directly to conscious awareness and do so
because they store memories that are expressed within
conscious experience.

Edelman's theory of consciousness makes a
distinction between two types of consciousness;
primary and higher-order. Primary consciousness is
coupled to ongoing sensory inputs and perception, and
in Edelman's model, normally depends heavily on the
interaction of the perceptual input stream with "a
special form of memory" that is located in cerebral
cortex. In Edelman's model, higher-order
consciousness is heavily dependent on the parts of the
brain involved with language behavior and, like
primary consciousness, is not independent of memory
processes. If consciousness is dependent on memory
processes then we need to be clear about the nature of
that dependence. We can also ask: is the ongoing
process of conscious experience is the SAME THING as
the ongoing process of using existing memories and
constructing new explicit memories? Is the purpose of
consciousness to be a system for making use of past
memories to control behavior and for controlling which
new explicit memories to form?

This line of thinking leads us to the idea that memory
and consciousness form a closed loop: our
consciousness is made possible by what we have learned
(depends on existing memories) and the purpose of
consciousness is to control the formation of new
memories. Does not such a closed loop introduce a
chicken-or-the-egg problem? In Edelman's theory,
this problem is solved by what Edelman calls the
"primary repertoire" of neuronal networks that are
able to be produced during embryonic development under
the guidance of our genes and independent of
interactions of the senses with an environment. In
Edelman's model, we are genetically endowed with
everything needed to make a basic neuronal network
that can start storing new memories and start
expanding our consciousness beyond the rudimentary
form of consciousness that we have prior to
interactions with an environment and prior to
learning.

We can use the visual system as an example. If a
mammal is prevented from being exposed to light during
early life, the visual cortex never develops the
complex neuronal networks required for normal visual
processing and visual awareness. Such an animal may
have a rudimentary consciousness of brightness and
darkness, but not the sort of vivid visual awareness
that is produced by a visual cortex that has learned
how to wire and function because of past sensory
inputs from a complex environment.

People almost always have a sensation that
consciousness is unified in a single instant of the
present. However, careful studies have been done which
show that various sensory inputs arriving over a range
of several tenths of a second can be experienced
within a single perceptual moment. The brain processes
that generate consciousness simply do not have a fine
time resolution. What we experience as the present is
actually a period of time that spreads out to include
the effects of brain activity that extends into our
immediate past. According to Edelman's model of
consciousness, we have essentially no consciousness
outside of what is generated by activation of neuronal
networks that have in the past stored memories. What
we experience as conscious awareness is almost
entirely constrained to ongoing patterns of cortical
activity that are memory in action. New sensory inputs
and ongoing patterns of memory activation resonate
with other existing stored memories to trigger yet
more new patterns of memory activation. In this view,
the contents of memory are the contents of
consciousness. What we experience as consciousness is
the remembered present. The remembered present is a
construct generated by our memory and some triggers
from new sensory inputs. In other words, utilization
of neuronal networks that have been shaped by past
experience (the circuits have stored memories) is what
we experience as conscious awareness of the present.
We literally remember what we experience as the
present. In this model of consciousness, second-to-second conscious experiences are not dependent on the
production of new long-term declarative memories, but
consciousness does depend on access to previously
stored memories.

So, back to the game in which I say a letter and you
immediately repeat it. Assume that people with normal
language function have a neuronal network that gives
them the capacity to hear another person say a letter
and then they can repeat it. How was that neuronal
network formed? Is it a simple network that could have
been genetically programmed and wired up during
embryonic development? Or is this network something
that has been heavily shaped and sculpted through past
experience, learning, and the storage of memories?
Some people seem to have the idea that consciousness
is built into a brain like the ability to show an
image is built into a computer monitor. Just turn it
on and consciousness shines out of a brain. However,
except for the rudimentary consciousness that is
produced by our basic genetically-programmed brain
structure, our consciousness is learned and is powered
by the activation of neuronal circuits where certain
memories are stored.

What about the purpose of consciousness and the idea
that new declarative memory storage is guided by
consciousness? We often think of the purpose of
consciousness in terms of our ability to exercise our
free will. If we are aware of things, then we can
decide to behave in certain ways. An alternative view
is that the purpose of consciousness is to allow a
special kind of adaptive utilization of stored
memories that is not possible for our procedural
memory systems. Our unconscious memory systems produce
adaptive behavior only when we engage in behavior. In
contrast, our explicit memory system can produce
adaptive behavior by functioning uncoupled from
ongoing behavior. The explicit memory system can
function in "virtual mode" by accessing and
combining memories without immediately producing
behavior. We use the explicit system to plan possible
behaviors. When used in "virtual mode", what is
produced is new explicit memory that can then be used
as the basis for actual behavior.

I wonder if consciousness evolved as a way of playing
with one's memories. The large bundles of neurons
connected to the visual cortex from our eyes and the
fact that our visual systems evolved to respond to the
outside world means that our consciousness normally
seems mostly concerned with sensory experience while
our conscious experiences during sensory deprivation
seem washed-out and pale in comparison. Our vivid
visual awareness is due to the adaptive importance of
paying close attention to visual sensory information.
We usually say that we are easy to distract visually.
Visual distractions can deflect our consciousness from
"deep thought" and planning. This is adaptive. If
danger is near we do not want to be "lost in
thought".

If we are making a plan, (for example, how to get a
piece of fruit before someone else does) we need to
constantly update our plan depending on what we see.
If we want to really think deep thoughts we either
isolate ourselves from visual distractions or we
create a set of visual cues that will guide our
thinking in a particular direction.

What about the details of how conscious experience is
generated? If the above view of dependence of
consciousness on memory is correct, then we need to
study the explicit memory circuits of the cerebral
cortex. Once we understand the memory circuits, I
suspect that the basis of conscious awareness will be
a rather trivial and unavoidable outcome of how those
memory circuits function.